System for regulating the idle speed of an internal combustion engine

Abstract

A system for regulating the idle speed of an internal combustion engine with an electronic fuel injection system having a bypass around a throttle valve of the engine and a solenoid operated control valve provided in the bypass to control the volume of air flow passing the bypass. The system comprises an engine speed sensor for sensing the engine speed of the engine and for producing an engine speed voltage, an idle switch responsive to idle operation of the engine for producing an idle signal, and a reference voltage circuit for producing a reference voltage corresponding to a predetermined idle speed. A first integrator is provided for integrating the difference between the engine speed voltage and the reference voltage and for producing a voltage. A control signal generating circuit is provided to be responsive to the voltage of the integrator for producing a positive going control signal and negative going control signal at upper limit and lower limit of the integrator output voltage. A second integrator is responsive to the positive going and negative going control signals to produce a control voltage. The control voltage is applied to a driver for energizing the solenoid of the solenoid operated control valve to actuate the control valve to regulate the idle speed to the predetermined idle speed.

What is claimed is: 
     
       1. A system for regulating the idle speed of an internal combustion engine with an electronic fuel injection system having a bypass around a throttle valve of the engine and a solenoid operated control valve provided in the bypass to control the volume of air flow passing the bypass, comprising: means for sensing the engine speed of said engine and for producing an engine speed voltage;   an idle switch responsive to the idle operation of said engine for producing an idle signal;   a reference voltage circuit for producing a reference voltage corresponding to a predetermined idle speed;   a first integrating circuit comprising an integrator for integrating the difference between said engine speed voltage and said reference voltage and for producing an output, and first switch means for causing said output to go to zero;   a control signal generating circuit comprising first and second comparators which are responsive said output of said first integrating circuit for producing switch actuating signals when said output reaches predetermined upper limit voltage and lower limit voltage repectively, second and third switch means reponsive to said switch actuating signals for producing a positive going control signal and a negative going control signal, and gate means responsive to said switch actuating signals for operating said first switch means;   a second integrating circuit responsive to said positive and negative going control signals for producing a control voltage; and   a driver responsive to said control voltage for energizing a solenoid of said solenoid operated control valve to actuate said control valve to regulate the idle speed to the predetermined idle speed.   
     
     
       2. The system for regulating the idle speed according to claim 1 wherein each of said integrators is formed by an operational amplifier and said driver comprises a transistor.